IS this a true EDI file that has passed through a clearinghouse or is a test file?

Does the HL * 1411 * ~ segment occur later in the file?

I could either modify the code so that HL loops that point to non-exist parent IDs can just parse as if it didn't have a parent ID, but if the parent ID appears later in the file this could be harder to do. But my understanding is the HL loops should be sequential.
Did the parser fail to see the HL * 1411 * segment earlier in the file?

Yes, it appears that it is pointing to a parent that is missing. I am surprised that you are getting this problem in production files. Though I have had a few others report this same problem.
There might be some validation tools available to help point out these type of syntax errors before you accept a file from your trading partner.

I am going to change the code to continue parsing this type of error, but throwing warning events so you know the file may not be valid. I'll update the discussion when the code is checked in.

I can't thank you enough for your help with this issue. In fact, this is not the first time you actually fixed the parser for syntax errors in production data I reported to you.

I have communicated your response back to our Trading partner. Hopefully, they will be able to correct this for future claims.

I can't express how grateful I am to you and this wonderful product you (and your team) has created.

In the true interest of open source, I can only pray that this product get more visibility and be widely accepted in the healthcare arena (if not already well-known in the industry). Thank you again, Sir.

I have updated
changeset 24814 to allow for parsing of the syntax error that you have.
Because this will no longer throw an exception on this error. Make sure that you have an event handler for the new ParserWarning event that I have added. This will allow you to identify files that are invalid. It will be up to you if you still want to process
and accept the file even with the bad syntax.

I have made one more change to
changeset 24841 that will actually make the default behavior throw exceptions as before. When you pass into the X12Parser constructor throwExceptionOnSyntaxErrors = false, this will have the new behavior that will throw warnings instead for both the missing
HL parent and for unrecognized segments.
This will keep the behavior the same for existing users, but allow them to switch over to warnings at their convenience. I will probably get a new release out within the week.